1. Field
The present invention relates to communications and, more particularly, to a method and system for carrying out a dynamic-routing service for routing voice calls to one of a plurality of associated subscriber terminals.
2. Description of Related Art
Recent advances in telecommunications technology have allowed a wide array of enhanced telecommunication services to be made available to subscribers. Examples of such services include abbreviated dialing, which allows a subscriber to reach a party by dialing less than the entire telephone number of that party; call forwarding, in which calls directed to the subscriber may be forwarded to another line; terminating call screening, which allows the subscriber to specify certain times during which all or selected incoming calls are to be rejected; and originating call screening, in which calls to certain telephone numbers are barred. In general, enhanced telecommunications services (“services”) encompass those call features that do more than simply place or terminate telephone calls as dialed.
To enable these services, telecommunications networks typically carry “signals” to set-up, maintain and tear down such communications in addition to voice and/or data content communicated between calling and called parties. These signals monitor the status of the lines, indicate the arrival of incoming calls, and carry the information needed to route the voice and/or data content through the telecommunications networks.
Most telecommunications networks use out-of-band signaling, i.e., the signals are transmitted over a signaling network that is separate from a circuit-switched network that carries the voice and data content. Thus, the signals carried on the separate signaling network are used to control the switches in the circuit-switched network to set up, maintain, and tear down the circuit between the calling and called parties. Currently, Signaling System 7 (“SS7”) is the most commonly used signaling system used to carry out these function.
In addition to SS7, most telecommunications networks in the United States have adopted an advanced intelligent network (“AIN”) standard approach to simplify signaling network architecture and provide a standardized messaging scheme. The AIN standards are embodied in Bellcore's AIN Release 0.1 and AIN Release 0.2.
Under the AIN approach, the switches do not have to have a great deal of “intelligence” built in to them, but rather, are focused on switching responsibilities. Control information and call processing logic for the switches, usually referred to as “service logic,” resides in one or more databases in a central network location instead of in the multitude of switches. This approach alleviates an otherwise significant burden on a telecommunications provider when updating services or adding new services to its telecommunications network. Instead of updating software and databases on all of its many switches, the telecommunications provider may update the databases at the central network location.
A service control point (“SCP”) provides an interface to these databases. The databases may reside within the SCP or other computers on the telecommunications network. Unlike the switches, the SCP has a great deal of intelligence (e.g., software, firmware, and/or hardware logic) built into it to carry out the service logic to control the multitude of switches.
The centralization at the SCP and the standardized message set allows an SCP to control a large number of switches, which are generally referred to as service switching points (“SSPs”) in AIN parlance. Using the standardized messages scheme, the SCP and the switches can exchange information to monitor the status of the lines, indicate the arrival of incoming and outgoing calls, and route the voice and/or data content, for instance.
The SSPs signal the SCP for guidance at predefined “trigger points” in the call processing. These triggers can occur either when the SSP is attempting to originate a call or attempting to terminate a call. The query signal from the SSP passes a set of relevant parameters, in a predefined format, to the SCP. Such parameters can include the calling party's telephone number and the called party's telephone number, for example. When the SCP receives the query, it executes the appropriate service logic and consults the appropriate databases to obtain the information and instructions needed to provide the intelligent network service. The SCP then sends a response message to the SSP instructing it how to complete the call and to provide the service.
Because of the large number of SSPs and other network elements connected to the signaling network, the signaling network typically includes one or more signal transfer points (“STPs”) that route the signals through the signaling network. Thus, the signals between SSPs and the SCP are often routed through one or more STPs. When SS7 signaling is used, signals may be routed to specific network elements based on their point codes. Alternatively, signals may be routed using global title translation (“GTT”), in which STPs route signals to their intended destinations without the need for point codes. In particular, when GTT is used, STPs route signals based on information contained in their payloads.
Wireless telecommunications networks have also been developed on a similar model. In wireless networks, switching is performed by mobile switching centers (MSCs). Each MSC typically controls one or more base stations or base transceiver stations (BTSs), sometimes via one or more base station controllers (BSCs). Each BTS provides a wireless coverage area within which mobile stations can communicate with the BTS over an air interface. The mobile stations can be cellular or PCS telephones, or other devices. Different formats may be used for communicating over this air interface. At present, the most commonly used formats in the United States are Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA), and Advanced Mobile Phone Service (AMPS).
Each mobile station typically has a “home” wireless network, in which a home location register (HLR) serves as a centralized repository of information about the mobile station. Typically, the HLR contains a service profile for the mobile station, the last reported location of the mobile station, and the current status of the mobile station, such as whether it is active or inactive. The service profile indicates the enhanced services the mobile station subscribes to.
Mobile stations typically identify themselves to wireless networks using one or more types of identification numbers. Each mobile station typically has a 10-digit Mobile Identification Number (MIN). The MIN may be, but need not be, the same as the directory number that would be dialed to reach the mobile station. Thus, a mobile station may also have a Mobile Directory Number (MDN) different from its MIN. Each mobile station also typically has a unique 32-bit Electronic Serial Number (ESN). Other identifiers, such as a mobile station identifier (MSID) and a mobile equipment identifier (MEID), may be used in addition to or in lieu of the MIN and MDN.
When an MSC needs to find information about a mobile station, such as where it is located or what services it subscribes to, it queries the HLR corresponding to that mobile station. Thus, to inquire about a mobile station that is roaming, i.e., operating on a network other than its home network, the MSC queries an HLR that is outside of its network. Typically, these queries are routed to the appropriate HLR based on the mobile station's MIN, MDN, MSID, MEID, etc. For example, the MSC may reference internal translation tables to determine which HLR to query for the MIN, MDN, MSID, MEID, etc, of the mobile station. Alternatively, STPs may route queries to the appropriate HLR using GTT, based on the MIN MDN, MSID, MEID, etc.
In a manner analogous to the AIN approach used in wireline networks, an MSC may also query a wireless intelligent network (WIN) SCP for call processing instructions, in the course of either originating a call from or terminating a call to the mobile station. Such queries can arise from trigger points set by the mobile station's service profile that the MSC downloaded from the mobile station's HLR. Moreover, an MSC uses such queries to obtain the call processing instructions needed to provide enhanced telecommunications services to the mobile station. In response to such queries, the WIN SCP will typically execute the appropriate service logic and consult the mobile station's service profile to formulate the call processing instructions that the WIN SCP then sends to the MSC.
The Telecommunications Industry Association/Electronics Industry Association (TIA/EIA) has developed a number of interim standards that specify how this signaling between MSCs, HLRs, WIN SCPs, and other network elements, should occur. In particular, most wireless networks in the United States use one of the revisions of TIA/EIA Interim Standard 41 (“IS-41”). The IS-41 signaling is typically run as an application on another signaling system, such as SS7. A recent revision of this Interim Standard, ANSI-41 Rev. D, which was published in July, 1997, is fully incorporated herein by reference. Furthermore, extensions to ANSI-41D or WIN triggers and WIN call processing are included in Interim Standard IS-771, which was published July, 1999, and is fully incorporated herein by reference.